I have this problem solved in a “stupid” way…. CONNECT HEADPHONES!
Couldn’t sleep for the same reason, tried thousand of solutions an then I ran swyh with… headphones connected. It worked brilliant!! It is Windows that changes your sound characteristic to play via laptop’s speakers. Connect headphones or anything into aux/phones connector and you will come across high quality sounds via DLNA. And finally I can hear spotify in a good quality. I think every windows 10 is affected. Couldn’t find any settings that would avoid changing of sound when played on internal speakers.
Now – looking for somebody to find how to cheat windows that headphones are connected.